Thiphene production from hydrogen sulfide and mono-olefin



Patented June 26, 1951 THIOPHENE PRODUCTION FROM HYDRO- GEN SULFIDE ANDMONO-OLEFIN Walter G. Appleby, Houston, and Albin F. Sartor, Pasadena,Tex., assignors to Shell Development Company, San Francisco, Calif., acorporation of Delaware No Drawing. Application June 17, 1946, SerialNo. 677,404

2 Claims. 1

This invention relates to the production of organic sulfur compounds andrelates more particularly to the production of unsaturated cyclicorganic sulfur compounds of the class consisting of thiophenes.

The unsaturated cyclic sulfur compounds containing the sulfur atom inthe ring, such as the thiophenes, are valuable as starting orintermediate materials in the production of a wide variety of productsincluding dyes, pharmaceuticals and many other chemical derivatives.Their production by methods disclosed heretofore, however, isuneconomical and beset with difiiculties which mitigate against theirpractical utilization on a large scale. Methods available heretofore fortheir synthesis under conditions resulting in the obtaining of athiophene product of sufiieient purity, without the simultaneousproduction in relatively large quantities of undesired by-products, aregenerally of so intricate or expensive a nature as to render themeconomically unattractive. Such methods, furthermore, rely upon theutilization as starting materials of substances not readily availableand the manufacture of which often renders subsequent production of thesulfur compounds therefrom highly uneconomical. Further inherentdisadvantages of many of these processes is the hazardous nature of thematerials used as initial starting material, as well as the poor yieldsthereby obtained. Other sources of these compounds, availableheretofore, include the byproducts of processes, the operatingconditions of which are directed to the production or processing ofmaterials other than thiophenes as the main product, and consequentlyare unreliable not only with respect to the amount but the nature andstate of purity of the compounds thus obtained.

It was found that thiophenes can be produced with substantially improvedefficiency by reacting a mono-olefin with hydrogen sulfide in thepresence ofv a solid catalytic material consisting essentially ofalumina, or an aluminous material, under well defined operatingconditions as disclosed and claimed in copending application Serial No.614,616 filed September 5, 1945.

It has now been found that unsaturated cyclic organic sulfur compoundsof the class con-' sisting of thiophenes are obtained from readilyavailable mono-olefins and hydrogen sulfide by reacting a monoolefinwith hydrogen sulfide in the presence of a .metal sulfide catalyst underthe Well defined conditions of the present invention. The highlyefficient and relatively i expensive process of the invention not onlybrings within the realm of practicability the large scale production ofthiophenes, but makes. possible such large scale production withunusually high yields. Not only can thiophenes be made to predominate inthe reaction products obtained while limiting the formation ofbyproducts to substantially only valuable hydrogen and carbon disulfide,but by selection of the particular mono-olefin charged, and control ofoperating conditions, liquid reaction products areobtained consistingsubstantially only of thio phenes. I

Mono-olefins suitable as starting materials for ,the process of theinvention comprise the nor,-

mally gaseous and normally liquid unsaturated hydrocarbons having atleast two carbon atomsto the molecule and containing a single olefinic';bond between two adjacent carbon atoms and: containing no other carbonto carbon unsatura-v tion. Suitable mono-olefins comprise for ex--:ample ethylene, propylene, butylene-l, butylene-2, isobutylene, theamylenes as pentene-l, pentene-Z, 2-methyl-butene-3, 2-=methyl-butene-l, 2-methyl-butene-2 and the hexylenes as. hexene-l, hexene-2,hexene-3, 2-methyl pentene-4, 2-methyl-pentene-3, 3-methyl-pentene- 4,2-methyl-pentene-l, 2-inethyl-pentene-2, 3-- methyl-pentene-Z,2,3-dimethyl-butene-1 and: 2,3-dimethyl-butene-2, the heptylenes, theoctylenes, the nonylenes, the decylenes, undecylenes= and the like. Themono-olefins may be further substituted by the replacement of one ormore of the hydrogen atoms by alkyl, aryl, aral-, kyl, cycloalkyl, orheterocylic groups, as well as halogens. The particular mono-olefinschosen 1 as charge material will of course be governed by the nature ofthe product desired. The hydrocarbon charge need not necessarily consistof a single mono-olefin, and two or more mono-.; oleflns may becomprised in the charge to the prooess. The hydrocarbon charge maycomprise materials other than the mono-olefins,- capable of acting asdiluents, temperature or flow controlling means, etc. Such materialswhich may be included in the hydrocarbon; charge comprise gases andvapors having no adverse effect upon the execution of the desired;reaction, such as, for example, normally gaseous and normally liquidsaturated hydrocarbons, nitrogen, hydrogen, carbon dioxide and the like.Suitable charge material comprises hydrocarbon mixtures or fractionscontaining substantial, amounts of the mono-olefins, such as, for eX-ample, the ethylene, propylene, butylene, am-

ylene in fractions obtained by fractionation of naturally occurringhydrocarbon mixtures or of products of refinery operations. Waste oroffgases, rich in mono-olefins, from many petroleum refinery operationsare particularly desirable starting materials for the process of theinvention.

The hydrogen sulfide to be reacted with the mono-olefin charge isintroduced into the system in admixture with the mono-olefins; or it maybe introduced in part, or in its entirety, in a separate stream to theinlet or any intermediate point or points of the reaction zone. Theratio of hydrogen sulfide to mono-olefins charged may vary within thescope of the invention. It is preferred, however, to add sulficienthydrogen sulfide to maintain a mole ratio of hydrogen sulfide tomono-olefins in the charge of at least 1:1 and not substantially inexcess of about :1. Still more preferably the mole ratio of hydrogensulfide to mono-olefins is maintained in the range of from about 2:1 toabout 6:1. Optimum results are obtained by maintaining the mole ratio ofhydrogen sulfide to mono-olefins at about 3:1 to 4:1, particularly whenutilizing normally gaseous mono-olefins as the hydrocarbon charge.Higher ratios of hydrogen sulfide may, however, be employed within thescope of the invention.

The hydrogen sulfide charged to the reaction need not necessarily bepure hydrogen sulfide and may comprise any suitable hydrogensulfide-containing gas or vapor, the components other than the hydrogensulfide of which have no substantial deleterious effect upon theexecution of the reaction. Thus the hydrogen sulfide may be employed inthe form of a gaseous mixture comprising the hydrogen sulfide inadmixture with a gas or vapor such as, for example, hydrogen, nitrogen,normally gaseous parafiins, etc. The gaseous component of the hydrogensulfide mixture may function to aid in maintaining the hydrogen sulfidewithin the prescribed concentration as well as to control conditions oftemperature, time of contact, etc.

In accordance with the process of the invention the mono-olefins, forexample the normally gaseous mono-olefins, such as the butylenes, arereacted with hydrogen sulfide in the presence of a suitable metalsulfide catalyst. Suitable metal sulfide catalysts comprise the sulfidesof the metals of the iron group, that is, those comprising a sulfide ofat least one of the metals of the group consisting of iron, cobalt andnickel. Although the sulfides of the iron group metals may be employedas such, particularly desirable catalysts comprise those containing thesulfide of at least one member of the iron group metals in combinationwith at least one of the metals of the left-hand column of group VI oftheperiodic table consisting of chromium, molybdenum, tungsten anduranium. Of these combination catalysts those containing at least thegreater part of the component consisting of the metal or metals of groupVI in the form of a sulfide or an oxide or in a mixture thereof areparticularly preferred. The combination of the group VI metals with thesulfides of the iron group, it has been found, obviates many of thedisadvantages normally interent in the use of the iron group sulfides bythemselves such as an undue degree of catalyst entrainment, lack ofcatalyst stability, as well as insufiicient physical strength towithstand handling without substantial attri- '4 tion. These catalystcombinations not only possess unusual stability and strength, but arehighly effective in catalyzing the interaction of the mono-olefins withhydrogen sulfide under the conditions defined herein with the formationof unsaturated sulfur-containing compounds consisting pre-dominantly andoften substantially completely of thiophenes. The use of the definedcombination catalysts in the process of the invention is thereforeparticularly advantageous in view of the relatively high yield ofthiophenes obtainable during prolonged periods of continuous operation.The proportions in which the sulfide of the metal or metals of the irongroup are combined with the sulfur and/or oxide of the metal, or metals,of the lefthand column of group VI of the periodic table, may varywidely within the scope of the invention. It is to be stressed, however,that the metals of group VI, by themselves, generally possess little ifany ability to promote or catalyze to any practical degree the formationof thiophenes from mono-olefins and hydrogen sulfide under the conditionof the present invention, and that their function in the process of theinvention, such as for example the obtaining of extremely long catalystlife with a relatively constant high yield is obtainable only when theyare employed in combination with a sulfide of a metal of the iron group.The combination catalysts may contain the sulfides and/or oxides of themetals of the left-hand column of group VI in such amounts that themetal of group VI in the combination catalyst is in the range of fromabout 0.5 to about by weight of the combined weights of the group VI andiron group metals in the catalyst.

The above-defined catalysts employed in the process of the invention,comprising the sulfide of the iron group metals alone and thosecontaining these sulfides in combination with at least one metal of theleft-hand column of group VI of the periodic table, are promoted by theaddition thereto of a member of the group consisting of the alkali andalkaline earth metals or compounds thereof. Particularly desirablepromoters are oxides of the alkali or alkaline earth metals, forexample, K20, NazO, BaO, SrO, LizO, CaO and the sulfides of thesemetals. Of these promoters the compounds, and particularly the oxide, ofpotassium are somewhat preferred. The promoters are preferably added insuch amounts that the ratio of alkali or alkaline earth metalconstitutes from about onehalf to about 10 percent, and still morepreferably from about 2 to about 7 percent by weight of the metal, ormetals, of the iron group present in the catalyst.

The invention is in no wise limited by the method of preparation of thecatalyst and it may be prepared in any suitable manner. The combinationcatalysts may be prepared by the simple expedient of effecting theadmixture of the several components. Thus suitable combination catalystsmay be prepared by admixing in finely divided form the sulfides of theiron group metals with the proper proportion of the oxides and/orsulfides of the group VI metals; or the members of the two respectivecomponent groups of the catalyst may be combined While one, or both, isin solution or suspension in a suitable liquid, the excess liquidremoved by filtration and/or evaporation and the resulting mixture driedat an elevated temperature. When a pro- 5. motercatalyst is employed itmay be incorporated into the catalyst by initial additional to one ormore of the "catalyst components, or to a'mixture of the componentsduring any stage of catalyst preparation. Catalysts possessing 'a highdegree of efficiency in the process of the invention are obtained bycombining all of the metal components in the form of oxides andthereafter subjecting the resulting mixed oxides to a, sulfidingoperation to effect the conversion of at least a substantial part of theiron group metal to the sulfide. The sulfiding operation may berexeouted under any suitable conditions assuring theconversion of atleast a substantial part! the iron group metal to the sulfide. Theextent to which any part of the oxide of the :group VI metal will beconverted to the sulfide during the sulfiding operation will of coursedepend upon the nature of the particular oxide "and group VI metalpresent, as well as the severity of the sulfiding operation. As statedabove, thegroup'VI metal component of the catalyst may be present aseither the oxide or the sulfidaor a mixture thereof. In preparingcatalyst 'for use .in the process of the invention by sulfiding themixed oxides, excellent results are obtained by effecting the sulfidingoperation under conditions leading to the conversion of at least asubstantial part :of the oxide of the'iron group metal to the sulfidewhile leaving at least a .part of :the "group metal in the form of theoxide. Because of the difiiculty if not impossibility in correctlydetermining the exact composition of a catalyst mixture obtained in thiswise, these combination catalysts obtained by sulfiding the mixed oxidesare referred to herein as"sulfidedoxide catalyst. By the term sulfidingas used throughout the specification and claims is meant thesuhjectionof the catalyst to a sulfur-containing atmosphere under conditionseffecting the conversion of at least a part of the catalyst componentsto the sulfide form. Suitable sulfiding conditions com prise theexposure of the catalystto a streamof a sulfur-containing gas, such as.for example, hydrogen sulfide, or a hydrogen sulfide-containing gas, atan elevated temperature. Suitable sulfiding temperatures comprise atemperature in the range of from about 500 C. to about 850' "0., andpreferably from about 550 C. to about 650 C. The hydrogen sulfide maybe'dilutedwith a suitable inert gas such as for example :nitrogen. Thefollowing example is illustrative of one method of preparing a sulfidedmetal oxide catalyst effective in the process of the invention.

Example I A mixture containing iron oxide, chromium oxide and potassium.oxide in the ratio of 892% :9.8 parts by weight, respectively, wasprepared by mixing in the proper proportions finely divided F6203 andCrzoa and adding thereto aqueous potassium carbonate to form a paste.The paste thus obtained was dried and heated at a temperature of about600 C. to effect the decomposition of the potassium carbonate to theoxide. The resulting mixture of oxides was thereupon sulfided by heatingin a stream-of hydrogen sulfide at a temperature of about 600 C. .toeffect the conversion of at least a substantial part of the iron oxideto the iron sulfide.

The efiiciency of the sulfidedmetaloxide catalysts above defined in theproduction of thiophenes in accordance with the process of the:invention is evidenced by the following example.

Example II A mixture of '1 -butylene and hydrogen sulfide containing amole ratio of hydrogen sulfide to butylene of 4:1 was passed over asulfided catalyst consisting of potassium promoted iron sulfide incombination with chromium oxide at a temperature of 600CL,atmosphericpressure, and a contact time of 15 seconds. The catalystused was obtained as described in "Example'I by heating :a mixturecontaining iron oxide, chromium oxide and potassium oxide in the ratioof :5:5 parts by weight, respectively, in a stream of hydrogen sulfideat a temperature of about 600 C. Efiiuence from the reactor was-passedsuccessively through a water cooled condenser, two cold traps maintainedat -50 C. to 60 C. and three caustic scrubbers. A conversion tothiophene based on butylene charged of about '13 percent was obtained togive a liquid product consisting o'f82percent by volumeof thiophene and18 percent by volume of carbon disulfide. No perceptible amount ofmercaptans was evidenced inthe reaction'products.

Catalysts, particularly catalysts of the sulfided metal oxide typeeffective in the catalytic productionof thiophenes in accordance withthe process of the invention are also obtained by'the method comprisingthe steps of coprecipitating the metals of the iron group together withthe metals of group VI, subjecting the resulting precipitate toconditions effecting the conversions of the metal to the oxide form, asby heating at an elevated temperature, if necessary, in the presence ofan oxygen-containing gas, and sulfiding the mixture of oxides thusobtained. Sulfided catalysts containing potassium-promoted iron andchromium of high efficiency in the process of the invention are obtainedby coprecipitating iron and chromiumfrom a mixed solution of ironsulfate and chromium nitrate with ammonium hydroxide, washing theprecipitate with potassium nitrate solution, drying the. precipitate ata temperature of from about C. to about C. andh'eating the driedprecipitate at a temperature of about 750 C. to effect the conversion ofthe metals to the oxides. The resulting mixture of oxides is thensubjected to sulfiding conditions in the presence of hydrogen sulfide ata temperature of about 600 C. to efiect the conversion of at least asubstantial part of the iron oxide to the-sulfide.

Suitable catalysts for use in the process of the invention which containat least a substantial part of both the iron group metal and the groupVI metal in the sulfided state include those, for example, wherein themetals of the iron group aswell as those of group VI are prepared underconditions involving the precipitation of the .meta'l-o'f the'iron groupin the sulfide form in the presence of sulfur compounds of the metals ofthe left hand column of group VI. Such methods of preparing these metalsulfide combination catalysts are exemplified by the following example.

Ercample III To an ammonium thiotungstate solution, prepared from anammoniacal aqueous tungstic acid solution with hydrogen sulfide, thereis added an aqueous solution oftnickel nitrate. A precipitate consistinglargely of "nickel sulfide is formed. Dilute sulfuric acid is addeduntil the hydrogen ion concentration of the resulting mixture, in termsof pH values, is in the range of from about 75 l toaboutZ. Tungstenisthereby precipitated as tungsten trisulfide. Theprecipitate isseparated from the liquor by filtration and/or centrifuging. Theresulting tungsten-nickel sulfides are dried and calcined at atemperature of from about 400 C. to about 42 C. in a hydrogenatmosphere, thereby effecting the conversion of tungsten trisulfide totungsten disulfide.

The high yield of thiophene obtained in accordance with the process ofthe invention executed with a metal sulfide combination catalystprepared by initial precipitation of the metal components as describedabove is illustrated by the following example.

Example IV A mixture of normal butylene and hydrogen sulfide containinga mole ratio of hydrogen sul-,- fide to butylene of 4:1 was passed overa nickeltungsten sulfide catalyst at a temperature of about 600 C.,atmospheric pressure, and a contact time of seconds. The catalystemployed was prepared substantially as described in Example III andcontained a weight ratio of nickel to tungsten of 122.24. Efiluence fromthe reactor was passed successively through a water cooled condenser,two cold traps maintained at C. to C. and three caustic scrubbers. Aconversion to thiophene based on butylene charged of 16 percent wasobtained to give a liquid product consisting a 48 percent by volume ofthiophene and 52 percent by volume of carbon disulfide. No perceptibleamount of mercaptans was evidenced in the reaction products.

The catalyst employed in the process of the invention may furthermore beused in admixture with solid diluent materials. Such diluent materialscomprise, for example, crushed firebrick, crushed silica, silica stone,charcoal, pumice, crushed sandstone, marble, majolica chips, ceramicbodies, porous aggregates as well as certain naturally occurringminerals as magnesite, brucite, and the like. Particularly desirablediluent or support materials comprise the highly porous materialspossessing adsorptive properties such as, for example, adsorptivealuminas or siliceous materials, the various adsorptive aluminas, theActivated Alumina of commerce bauxite, adsorptive magnesia and the like.The

use of a support or diluent material is preferablyresorted to whenemploying the catalysts consisting essentially or predominantly of onlythe sulfides of the metals of the iron group. The support material maybe combined with the catalyst in any suitable manner. It may be combinedwith the catalyst by simple admixture or the metal sulfide may bedeposited or formed uponthe support material. Preparation of suitablecatalysts comprising a sulfide of a metal of the iron group incombination with an adsorptive material is exemplified by the followingexample.

Example V hydrogen sulfide for a period of about two hours toconvert-the iron to the sulfided form.

The effectiveness of the catalysts, comprising only the sulfide of themetals of the iron group, in catalyzing the interaction of hydrogensulfide and mono-olefins with the production of a thiophene reactionproduct is evidenced by the following example:

Emample VI A mixture of normal butylene and hydrogen sulfide containinga mole ratio of hydrogen sul-' fide to butylene of 4: 1 was passed overa catalyst consisting of iron in the sulfided form deposited uponadsorptive alumina, at a temperature of 600C., atmosphere pressure, anda contact time of 15 seconds. The catalyst was prepared as described inExample V and had an iron content of about 7 percent by weight. Aconversion to thiophene, based upon butylene charged, of 31.4 percentwas obtained to give a liquid product consisting of 94 percent by volumeof thiophene and 6 per cent by volume of carbon disulfide. Noperceptible amount of mercaptans was evidenced in the reaction product.

\ 'A critical factor in the execution of the process of the inventionresides in the temperature employed. maintained above about 550 C. andpreferably not substantially above 800 C. At lower temperatures theformation of reaction products predominating in sulfur compounds otherthan the desired thiophenes is generally favored. Tempe'r'atures above800 C. are generally deleterious to catalyst activity as well as theyields obtained.

It is preferred to maintain the temperature in a range of from about 575C. to about 675 C.

' Still more preferred, particularly when charging normally -gaseousmono-olefins, for example,

normally-gaseous hydrocarbons comprising alonger-r'duration may howeverbe resorted to within the scope of the invention.

The process of the invention is carried out at subatmospheric,atmospheric or superatmospheric pressures. It is preferred, however, tomaintain the pressure below the combined vapor pressures of theconstituents of the reaction mix-'- ture. The use of a pressure in therange, for ex-- ample, of from-about atmospheric pressure to about 500pounds per square inch absolute is particularly preferred.

Under the above-defined conditions excellent conversions of mono-olefinsto thiophenes are obtained with long catalyst life. Thus the reaction ofbutylene with hydrogen sulfide under these conditions will result in theproduction of a liquid product consisting essentially only of thiophene.Contrary to results obtainable utilizing processes disclosed heretofore,the final products of the invention are substantially free ofmercaptans.

The process of the invention is executed in any suitable type ofapparatus enabling efiicient contact of reactants with the catalyst.Hydrogen sulfide and unreacted hydrocarbons are sepa-' rated from thereactor efiluence by any suitablemeans and recycled to the reactionzone. Prodi uct separation may comprise such steps as, for example,solvent extraction, distillation, extractive disillation, adsorption andthe like.

'Theprocess of the invention is executed in batch,'semi-continuous orcontinuous operation.

Thus the temperature of reaction isv A contact time of from about 10 to30- The reaction zone may include a plurality of separate reactorsconnected in series or in parallel When a plurality of reactorsconnected in series are employed, all or a part of the reaction productsmay be separated from reactor eifluence prior to introduction of thestream into the subsequent reactor of the series. Conditions within thereactors may be controlled to favor the production of thiophene in allof the reactors or they may be controlled to favor the production ofhydrogen in one or more of the reactors.

The catalysts employed in the process of the invention may be subjectedprior to use, or between on-stream periods, to a flushing operation witha suitable gaseous material, such as for example nitrogen, hydrogen,saturated hydrocarbons or the like, followed by a sweeping with hydrogensulfide, or a hydrogen sulfide-containing gas. This pretreatment ispreferably executed at an elevated temperature in the range of, forexample, from about 400 to 750 0., and preferably in the range of fromabout 550 to about 650 C. The catalysts of the invention maintain theiractivity over prolonged periods of time under the conditions ofoperation of the process. When activity falls below that commensuratewith practical or optimum operating conditions, the catalysts aresubjected to a suitable regeneration treatment. Suitable regenerationconditions comprise such steps as the sweeping of the catalyst with aninert gas such as nitrogen, followed by passage therethrough of oxygenor an oxygencontaining gas. The regeneration is preferably effected atan elevated temperature preferably in the range outlined as suitablepretreating temperatures. The resulting regenerated catalysts arepreferably pretreated prior to use as described above The invention is,however, not limited to any particular method employed in thepretreatment and/or regeneration of the catalysts.

We claim as our invention:

1. The process for the production of thiophene which consists ofcontacting a mixture of butylene and hydrogen sulfide containing a molarratio of hydrogen sulfide to butylene of from about 2:1 to about 6:1with iron sulfide at a temperature of about 550 to about 800 C. in areaction zone for a time between 1-0 and 30 seconds, thereby reactinghydrogen sulfide with butylene with the formation of thiophene in saidreaction zone, separating thiophene and unconverted hydrogen sulfidefrom the resulting reaction products and recycling said unconvertedhydrogen sulfide to said reaction zone.

2. The process for the production of a thiophene which consists ofcontacting a mixture of hydrogen sulfide and a normally gaseousmonoolefin containing'a molar ratio of hydrogen sulfide to olefin offrom about 2:1 to about 6:1 with iron sulfide at a temperature of about550 to about 800 C. in" a reaction zone for a time between 10 and30seconds, thereby reacting hydrogen sulfide with said olefin with theformation of thiophene in said reaction zone, separating thiophene andunconverted hydrogen sulfide from the resulting reaction products andrecycling said unconverted hydrogen sulfide to said reaction zone.

WALTER G. APPLEBY. ALBIN F. SARTOR.

REFERENCES CITED The following references are of record in the file ofthis patent:

, UNITED STATES PATENTS Number OTHER REFERENCES Dufiey, Ind. Eng. Chem,26, 91-92 (1934). Maihle, Chimie 8a Industrie, 31, 257 (1934).

1. THE PROCESS FOR THE PRODUCTION OF THIOPHENE WHICH CONSISTS OFCONTACTING A MIXTURE OF BUTYLENE AND HYDROGEN SULFIDE CONTAINING A MOLARRATIO OF HYDROGEN SULFIDE TO BUTYLENE OF FROM ABOUT 2:1 TO ABOUT 6:1WITH IRON SULFIDE AT A TEMPERATURE OF ABOUT 550* TO ABOUT 800* C. IN AREACTION ZONE FOR A TIME BETWEEN 10 AND 30 SECONDS, THEREBY REACTINGHYDROGEN SULFIDE WITH BUTYLENE WITH THE FORMATION OF THIOPHENE IN SAIDREACTION ZONE, SEPARATING THIOPHENE AND UNCONVERTED HYDROGEN SULFIDEFROM THE RESULTING REACTION PRODUCTS AND RECYCLING SAID UNCOVERTEDHYDROGEN FULFIDE TO SAID REACTION ZONE.